In the Church of Difficult Music

They trickled in to an anonymous, mostly shuttered storefront on a rugged corner at Avenue C and Second Street, prompting occasional confusion from pedestrians walking by. They were entering a place of almost spartan simplicity: a dimly lit chamber with a brick wall and folding chairs, and no food or alcohol served. They paid $15 cash to a man seated inside.

Shortly, Rudresh Mahanthappa’s Bird Project, a quartet, took the small performance floor to play contemporary interpretations of classic Charlie Parker tunes so evolved that the original melodies were nearly unrecognizable.

This is the Stone, which some regard as the purest musical space in New York. It is a landmark site for avant-garde and experimental music, and it is as sparse as a single note played repeatedly on a piano. But the sounds that leak from its shuttered windows are the opposite of such austerity. Rather, they are as varied and unpredictable as a spiraling Ornette Coleman solo.

It was founded in 2005, and performances have ranged from guitarists abusing their instruments to world musicians jamming in confounding time signatures to string quartets. Workers are unpaid volunteers. All ages can enter. The backstage area is a plain basement. All proceeds from admission go directly to the musicians.

It is also considered, among its fans, a pinnacle of what such a music space should be. Its sparseness is deliberate, intended to sharpen focus on the music and nothing else, and fans like it that way.

“Anything honest, sincere, imaginative, adventurous, that maybe falls through the gaps, has happened here,” said the downtown composer and avant-garde leader John Zorn, who is the Stone’s artistic director. “This is music that is loved by musicians.”

Of the Stone’s spareness, he said: “It’s all about the music, and that’s all that happens. There are no distractions.”

Artists like the guitarists Marc Ribot and Fred Frith, the composer Ikue Mori and the pianist Sylvie Courvoisier are regulars at the Stone. Recently, the alternative-rock heroes Thurston Moore and Lee Ranaldo, the guitarists of Sonic Youth, performed together, drawing a large crowd, although they did not play anything radio-friendly. Over the rhythms of abstract drumming, Mr. Moore coaxed jet-engine roars from his guitar and Mr. Ranaldo massaged a drumstick behind his guitar’s neck, generating rippling feedback.

The space holds a unique position in New York, Mr. Moore said. “It’s the most critical listening room in the city, as far as experimental music is concerned,” he said. “You’re bringing your A-game.”

On the night the Bird Project performed, Mr. Mahanthappa, the saxophone-playing bandleader, soloed prodigiously beside a space heater through a cascading flurry of notes from his band. Watching in the darkness was Maurice Edwards, 57, a self-proclaimed Stone “usual suspect,” who has frequented the place for years.

“The set-up here is tailor-made for people for one thing only: to listen to musicians perform,” he said. “And I don’t have a problem with that.”

In the front row was Eric Reiner, 22, who came to see the band without knowing the history of the Stone. He was initially surprised that he couldn’t buy a drink here. But during an intense improvisation he found himself rapt and laughing aloud. “This place feels like you’re dreaming,” he said after the set was over. “It’s like you’re in your own head.” The bareness, he added, heightened his experience. “The music was the only thing I could focus on,” he said. “My brain was completely engulfed.”